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Perceptual Constancies

Perceptual Constancies. Unit 1 Psychology – Visual Perception. What are perceptual constancies?. In vision, perceptual constancy refers to the tendency to perceive an object as remaining stable and unchanging (‘constant’) despite any changes that may occur to the image cast on the retina.

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Perceptual Constancies

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  1. Perceptual Constancies Unit 1 Psychology – Visual Perception

  2. What are perceptual constancies? • In vision, perceptual constancy refers to the tendency to perceive an object as remaining stable and unchanging (‘constant’) despite any changes that may occur to the image cast on the retina. • Three perceptual constancies involve size, shape and brightness.

  3. Size Constancy • Size constancy involves recognising that an object's actual size remains the same, even though the size of the image it casts on each retina changes. For example, when you are on a railway station platform watching a train coming towards you, the image it casts on each retina gets progressively bigger. However, you do not perceive the train as actually increasing in size.

  4. Size Constance examples • http://www.youtube.com/watch?v=XOarD0DhhdM Puffing Billy • http://www.youtube.com/watch?v=OxYQwgXc-sM (Subaru Impreza add)

  5. Shape Constancy • Shape constancy is the tendency to perceive an object as maintaining its shape despite any change in shape of the image of the object on the retina.

  6. How does Shape Constancy work? • As we move around in our daily lives, the angles at which we view objects change. Consequently, the image of the object that is cast on the retina also changes. • If we interpreted the image in terms of how it actually occurs on the retina, the object would be perceived as constantly changing shape. • However, by automatically using the principle of shape constancy we know that the object hasn't changed shape and we perceive it as remaining stable (constant).

  7. Example – Road Signs As we drive along the road we come across many road signs. Even if we cannot make out the wording on a sign, because it is too far away, we are able to identify what it is. Despite the enormous change in size of the retinal image of a road sign as we travel along, our familiarity with road signs allows us to hold a stable perception of each sign at almost any distance. We do not perceive a sign to actually get bigger as we get closer to it and to shrink as we get further away.

  8. BOX 3.7: Strategic deception involving size constancy • Interesting tactic used by the Allies against the German’s in the second world war

  9. Brightness Constancy • Brightness constancy is the tendency to perceive an object as maintaining its level of brightness in relation to its surroundings, despite changes in the amount of light being reflected from the object to the retina.

  10. Example • Suppose you are seated in a room at dusk with overhead lighting on. Suddenly, the electricity supply is cut off. Despite the changed lighting conditions, you still perceive the objects around you as remaining the same colour. You know, for example, that the cover on the lounge chair hasn't suddenly become dull even though there is a reduction in brightness (‘light intensity’) on the image produced on the retina and it ‘looks’ duller. Because everything in your immediate environment has been reduced in light intensity by the same amount, the colours of all objects are perceived with the same brightness as they were before the lights went off.

  11. LEARNING ACTIVITY 3.19 • Please Complete LA 3.19

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